File this one under "stuff that drives you crazy about Flash". I spent hours troubleshooting this, so hopefully this simple explanation will be useful to someone else. The short of it is, Flash will not apply "Advanced Anti-Aliasing" to text fields that are flipped. This causes a large variancein tracking between letters and which results in a different length for the text field (yes it is recorded in their voluminous, an often unhelpful, documentation, if you happen to look up the right combination of keywords).

We recently launched some new free design skin templates for our Gutensite clients, one of which included a dynamic text field for the client's name. There is limited space in the design, so we made an elegant Actionscript function to decrease the font of the text field until the name fit within the specified width and height of the text area. This way long names will fit in the area, albeit at a smaller font size. Simple stuff, it works well.

However, to complicate matters, this design needed to put a fake "reflection" of the name below a horizon line. So we simply made two text fields, with identical content, and flipped the second one upside down (transform > flip horizontal, or manually _yscale = -100).

But we observed the oddest phenomenon. The letters in the second text field, didn't quite line up with the letters of the top text field, in fact they were off sometimes by 20px or more. And for the effect to work, of course the letters needed to line up perfectly, giving the illusion of a reflection. To make a long story short, the reason for this discrepancy is due to Flash's "Advanced Anti-Aliasing". It turns out, that it won't work if the text field is flipped. And so the flipped text field, defaults to "Anti-Aliasing for Animation" and with different anti-aliasing, the tracking between letters is thrown off. 

Now I'm sure most people would never notice the slight difference in tracking, if the field stood by itself. But because we transposed both versions one above the other, it was dreadfully obvious. In case you are wondering, it does not help to put the text field right side up in a movie, and then flip the movie. Flash still sees this as a flipped text field.

So of course the solution is that we had to make both fields use "Anti-Aliasing for Animation". It doesn't look as nice, but it works. That's the sacrifice people will have to make to have a template site I suppose, there will always be small sacrifices, as opposed to customizing the design from start to finish without the need to adjust for dynamic content.